The present invention relates to an improved drive for the ignition distributor of an internal combustion engine, in association with a lubrication pump drive.
In conventional internal combustion engines with a camshaft arranged laterally in the cylinder block, the camshaft drives an intermediate shaft disposed substantially perpendicularly to it, through the agency of helical gearing, the bottom end of the intermediate shaft being connected to a lubrication pump and the top end to a distributor shaft.
In these known distributor drives, because of the 1:1 transmission ratio of the helical gearing, which is always required, difficulties were encountered when toothing errors occurred, and these led to increased wear and noise in the distributor drive.
In more modern internal combustion engines with a camshaft located at the top of the cylinder head, in other words over-head camshaft engines, a layshaft located laterally in the cylinder block was provided and this was driven through the camshaft drive, at the same speed as the camshaft. This layshaft also, through the agency of helical gearing, drove an intermediate shaft extending substantially perpendicularly to it, the bottom end of which was once again connected to a lubrication pump and the top end to a distributor shaft.
Here, again, because the layshaft was driven at the same speed as the camshaft, a transmission ratio 1:1 through the helical gearing was required, and again, in the event of toothing errors this tended to lead to wear and noise problems in the distributor shaft drive.
Moreover, a relatively large amount of constructional outlay was necessitated by the arrangement and the driving of the layshaft, so that even in more modern engines using an overhead camshaft, this kind of layshaft was as far as possible avoided.
This led, in a recently developed internal combustion engine with an overhead camshaft, to the separation of the lubrication pump drive and the ignition distributor drive, the lubrication pump being arranged directly on the crankshaft in accordance with German Published Patent Application DT-OS 1,576,345 and being driven thereby, and the distributor being arranged in direct extension of the camshaft and being driven directly by the latter.
The arrangement of the lubrication pump directly on the crankshaft resulted in a highly favorable situation, without any unwanted disadvantages, from the point of view of constructional outlay.
The arrangement of the distributor in direct extension of the camshaft, although highly favorable from the point of view of constructional outlay, nevertheless had the drawback that the operation of the distributor could on occasion be severely impaired due to the substantial level of torsional vibration occurring in the camshaft.
It was discovered in this context that in the conventional distributor drive arrangement, which simultaneously drove a lubrication pump, a highly desirable effect arose, namely that the lubrication pump acted as proportional vibration damper, the absence of which in the later systems caused serious problems.